The present invention relates generally to optics, optical fibers, and optical systems and devices. The present invention also relates to a multi-function optical fiber system.
Multi-function laser-based systems are employed for a variety of purposes. For example, it has been suggested to provide up to seven different laser-based equipment systems in combination, including the following: (1) a laser range finder; (2) an infrared aim light; (3) an infrared illuminator (a flashlight); (4) a visible aim light; (5) a visible bore light (a mandrel boresight laser for aligning sights); (6) a combat identification system; and (7) a multiple integrated engagement system for laser-tag simulated exercises.
Prior art multi-function laser-based systems are generally complex and bulky. There is a need in the art for a system in which components are combined and/or eliminated to reduce complexity, cost and overall weight. In particular, there is a need for an optical system which provides multiple functions with a reduced number of optical sources and/or other components. As the number of components in such systems are reduced, however, it becomes difficult to provide sufficient optical power for certain functions. Thus, there is also a need in the art for a system that efficiently receives and transmits light energy, using a reduced number of components.
The disadvantages of the prior art are overcome to a great extent by the present invention. The present invention relates to an optical fiber that has a core and at least first and second claddings. The core is used to transmit one or more first light signals in a first direction. The first, inner cladding is used to transmit a second light signal in the opposite direction. The second cladding is used to confine the second signal in the first cladding. A notch, prism or other suitable device, extending into the first cladding, is used to direct the second signal into a second, input/output fiber.
According to one aspect of the invention, the index of refraction of the core is greater than the index of refraction of the first cladding, and the index of refraction of the first cladding is greater than the index of refraction of the second cladding.
According to another aspect of the invention, the transmission fiber may be a double-clad optical fiber designed for single mode operation in the 1550 nanometer wavelength range. The diameter of the core in the transmission fiber is preferably less than about ten microns, and the second cladding may be a buffer layer formed of polymeric material.
The present invention also relates to an optical system made up of a single mode optical transmission fiber, a multi-function signal generating system for launching a wavelength multiplexed transmission signal into the fiber core, and an input/output fiber for receiving a return signal from the cladding of the transmission fiber. According to this aspect of the invention, the core of the input/output fiber has a greater diameter than that of the transmission fiber.
According to another aspect of the invention, the transmission fiber has a reflective surface for directing the return signal out of the first cladding and into the core of an input/output fiber. The reflective surface (which may be in the form of an air/glass interface) may be located in a portion of the first cladding. The reflective surface preferably does not intersect the core of the transmission fiber.
According to yet another aspect of the invention, the return signal is detected at the distal end of the input/output fiber. The detection of the output signal may be correlated with other operational signals to determine a desired parameter, such as the distance to a target, for example.
According to yet another aspect of the invention, a second laser light source may be provided for supplying additional light energy into the transmission fiber. The additional light energy may be coupled into the first cladding of the transmission fiber, where it may be used to augment an outgoing beam that is collimated by a lens device. If desired, the lens device may be same one that is used to converge the return beam onto the outgoing end of the transmission fiber.
The present invention also relates to a method of operating an optical system. According to a presently preferred method, a first light signal (which may be a wavelength multiplexed signal) is propagated through a core of a single mode transmission fiber. A second light signal (which may be a reflected portion of the first signal) is simultaneously propagated through a cladding portion of the transmission fiber in the opposite direction. The second signal is reflected into a large diameter core of a multi-mode input/output fiber. In addition, the same reflective surface may be used to reflect additional light energy into the cladding of the transmission fiber.
According to one aspect of the invention, the optical system may be mounted on a hand-held aimable device, such as a rifle or binoculars. As such, the direction of the outgoing beam, as well as the origin of the return beam, may be determined by the direction in which the aimable device is aimed.